Wireless systems are susceptible in many respects. These susceptibilities are increasing as new wireless technologies are growing in prevalence. Ad-hoc networks, where individual users communicate with each other directly without using intermediary network nodes, creates new susceptibilities to the users and networks. These susceptibilities can be categorized as “trust”, “rights”, “identity”, “privacy” and “security” related issues.
“Trust” refers to the assurance that information communicated in these systems can be shared. To illustrate, a wireless user may want to know that a communication was sent to it from a trusted source and using trusted communication nodes. The user in an ad-hoc network may have no knowledge that the communication was transferred over a hacker's wireless device with packet sniffing software. Additionally, with the use of tunneling, intermediate nodes transferring the communication may be transparent to the wireless user.
“Rights” (“rights management”) refers to the control of data. To illustrate, one wireless user may have limited rights in a wireless system. However, if that user colludes (knowingly or unknowingly) with a second node having superior rights, that user may gain rights above those that the user is allowed.
“Identity” refers to the control linked to the identity of the wireless user. To illustrate, a rogue wireless device may attempt to access a wireless network by pretending to be an authorized user of the network, by using that authorized user's identity. “Privacy” refers to maintaining privacy of the individual, data and context. A wireless user may not want others to know, which web sites he/she visits and, in particular, information sent to these sites, such as financial, medical, etc. “Security” refers to the security of the data and context, such as preventing an unauthorized individual access to a wireless user's information.
To reduce the susceptibility of wireless networks, various techniques are used. Although these techniques provide some protection, they are still susceptible to the trusts, rights, identity, privacy and security issued. For example, although a particular wireless communication node may have the correct keys to communicate with a wireless user, that user may not know whether the node can be trusted.
Additionally, authentication of the user using these keys typically occurs at higher layers of the communication stack. Accordingly, even when these controls are in place, a rogue wireless user or hacker may have some (although limited) access to the communication stack. This access creates vulnerabilities, such as to denial of service attacks, among others.
Steganography is the art of passing information in a manner that the very existence of the message is unknown. The goal of steganography is to avoid drawing suspicion to the transmission of a hidden message. If suspicion is raised, then this goal is defeated. Steganography encompasses methods of transmitting secret messages through innocuous cover carriers in such a manner that the very existence of the embedded messages is undetectable. Creative methods have been devised in the hiding process to reduce the visible detection of the embedded messages.
Watermarking is a well-known technique for protecting and tracking digital information, which has been successfully exploited in the area of music and video data storage and communication. The traditional framework for watermarking consists of three elements: 1) cover signal s, 2) watermark w, 3) embedding function E and 4) secret key k. The watermarked signal is then defined as sw=Ek{s,w}. The watermark carrying signal sw must be robust to common signal processing operations such as filtering, compression or any other operation that are the basic functionalities of the network. Robustness is defined by the ability to extract the watermark from an altered signal. The second requirement of any watermarking scheme is imperceptibility, (i.e., the difference between s and sw must not alter the operation of the system in any perceptible manner). The watermark must also be transparent in the sense that the watermark-unaware portions of the network must be able to process sw without additional hardware or software. The watermark must also be secure even though the watermarking algorithm itself may be public. This security is frequently achieved through a secret key that is exchanged with the receiver through some form of secure key exchange.
In the prior art, the concept of digital watermarking is used in information assurance and User Authentication. A watermark is embedded into the user data, which is then transported by the physical layer of the communication link. The recipient extracts the watermark and compares it with a local copy to authenticate the transmitter.
Watermarks and signatures are techniques for adding metadata or unique information to media for signaling and/or security purposes. To reduce these susceptibilities to wireless communications, it is desirable to have alternate approaches to watermarking and adding signatures to wireless communications.